Pile foundation detection method based on ultrasonic waves

Abstract

The invention relates to the technical field of pile foundation detection, in particular to a pile foundation detection method based on ultrasonic waves, which comprises the following steps: after a pile body is prepared, standing for a first preset duration, and carrying out ultrasonic detection, when it is judged that the preparation of the pile body does not meet the preset standard according to the energy attenuation characterization value, whether the preparation of the pile body meets the preset standard or not is secondarily judged according to the waveform characterization value, or whether the preparation of the pile body meets the preset standard or not is judged according to the waveform characterization value; determining the reason that the preparation of the pile body does not meet the preset standard according to the amplitude recovery rate; when it is judged that preparation of the pile body meets the preset standard according to the energy attenuation characterization value, bearing platform pouring is conducted; when it is judged that the preparation of the bearing platform does not meet the preset standard according to the compactness characterization value, the concrete pouring rate is reduced or pouring is stopped, and early warning is given out, so that the ultrasonic detection precision is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of pile foundation detection, and particularly to a pile foundation detection method based on ultrasonic waves. Background Art

[0002] A pile foundation is a deep foundation jointly composed of piles and a pile cap connecting the pile tops. Its core function is to transfer the building load to a harder bearing layer underground through the pile body, thereby improving the bearing capacity and reducing the settlement risk.

[0003] Ultrasonic detection penetrates the pile body by emitting high-frequency elastic pulse waves, and the receiving end records the changes in wave velocity, wave amplitude, and waveform characteristics. When there are defects in the concrete, such as holes or honeycomb structures, the ultrasonic waves will be reflected, scattered, or attenuated. By analyzing the signal anomalies, the integrity of the pile body can be judged.

[0004] However, the dynamic changes in the physical properties during the concrete solidification process are not fully considered. If the detection is carried out too early before the final setting state, misjudgment will occur due to the instability of the concrete material. At the same time, it is difficult for conventional detection to distinguish between pseudo-defects caused by insufficient setting time and real structural defects, resulting in a lack of pertinence in subsequent treatment measures. In addition, the monitoring of the compactness during the pile cap pouring stage mostly relies on manual experience or a single parameter threshold, and the construction parameters cannot be dynamically adjusted, resulting in low detection efficiency. Chinese Patent Application Publication No.: CN119355132A, discloses a bridge pile foundation defect detection system based on ultrasonic technology, including: a control terminal for controlling and managing the overall operation process of the system and performing real-time monitoring of data; a multi-channel high-frequency ultrasonic detection module for emitting ultrasonic signals through a multi-channel high-frequency probe array and receiving the reflected signals inside the bridge pile foundation to form original detection data; a parallel computing and 3D imaging module for performing parallel computing processing on the received ultrasonic signal data and generating a three-dimensional structure imaging inside the bridge pile foundation. Through the combination of the multi-channel high-frequency ultrasonic detection module with phased array technology and multi-reflection wave processing technology, high-precision detection of the internal structure of the bridge pile foundation is achieved.

[0005] It can be seen that the above technical solutions do not consider the influence of the static time of the pile body and the final setting time of the concrete on ultrasonic detection, resulting in misjudgment in ultrasonic detection; at the same time, a grading early warning mechanism based on the compactness characterization value is not introduced during the pile cap construction stage, and the formation of through defects cannot be prevented, resulting in the problem of low ultrasonic detection accuracy in the construction process. Summary of the Invention

[0006] To this end, the present invention provides a pile foundation detection method based on ultrasonic waves to overcome the problems in the prior art that the influence of the static time of the pile body and the final setting time of the concrete on ultrasonic detection is not considered, resulting in misjudgment in ultrasonic detection; at the same time, a grading warning mechanism based on the compactness characterization value is not introduced during the construction stage of the bearing platform, and the formation of through defects cannot be prevented, resulting in low accuracy of ultrasonic detection in the implementation of the construction process.

[0007] To achieve the above object, the present invention provides a pile foundation detection method based on ultrasonic waves, including: After the pile body is prepared, it is left static for a first preset time, and ultrasonic detection is carried out to obtain the amplitudes of several detection zones of the pile body provided with several detection zones, and the energy attenuation characterization value is obtained. When it is determined according to the energy attenuation characterization value that the preparation of the pile body does not meet the preset standard, the waveform peak value of the ultrasonic first wave is collected and the waveform characterization value is obtained, and the pile body is left static for a second preset time to obtain the amplitude of the pile body and the amplitude recovery rate is obtained. According to the waveform characterization value, it is determined secondly whether the preparation of the pile body meets the preset standard, or according to the amplitude recovery rate, the reason why the preparation of the pile body does not meet the preset standard is determined, and the reasons include that there are holes in the pile body or the energy attenuation characterization value has a deviation. When it is determined according to the energy attenuation characterization value that the preparation of the pile body meets the preset standard, the bearing platform is poured. The sound velocities of each detection point of the bearing platform are obtained, the compactness characterization value of the bearing platform is obtained, and when it is determined according to the compactness characterization value that the preparation of the bearing platform does not meet the preset standard, the concrete pouring rate is reduced or the pouring is stopped and a warning is issued.

[0008] Further, it is determined whether the preparation of the pile body meets the preset standard according to the energy attenuation characterization value, wherein, If the energy attenuation characterization value is less than the first preset energy attenuation characterization value, it is determined that the preparation of the pile body meets the preset standard and the bearing platform is poured; If the energy attenuation characterization value is greater than or equal to the first preset energy attenuation characterization value and less than the second preset energy attenuation characterization value, it is determined that the preparation of the pile body has a tendency not to meet the preset standard, and it is determined secondly whether the preparation of the pile body meets the preset standard according to the waveform characterization value; If the energy attenuation characterization value is greater than or equal to the second preset energy attenuation characterization value, it is determined that the preparation of the pile body does not meet the preset standard, and the reason why the preparation of the pile body does not meet the preset standard is determined according to the amplitude recovery rate.

[0009] Further, the energy attenuation characterization value is the standard deviation of the amplitudes corresponding to several test points, wherein the test points are all arranged on the detection zones evenly distributed along several radial directions of the pile body.

[0010] Further, determine the reason why the preparation of the pile body does not meet the preset standard according to the amplitude recovery rate of the pile body, where if the amplitude recovery rate is less than the preset amplitude recovery rate, it is determined that the reason why the preparation of the pile body does not meet the preset standard is that there are holes in the pile body, and increase the vibration frequency of the pile body according to the difference between the amplitude recovery rate and the preset amplitude recovery rate; if the amplitude recovery rate is greater than or equal to the preset amplitude recovery rate, it is determined that the reason why the preparation of the pile body does not meet the preset standard is that the first preset duration is less than the final setting duration of the concrete of the pile body, resulting in deviation of the energy attenuation characterization value obtained by ultrasonic testing.

[0011] Further, there are several frequency increasing methods for increasing the vibration frequency of the pile body, and each frequency increasing method has a different amplitude of increase in the vibration frequency of the pile body.

[0012] Further, the process of obtaining the amplitude recovery rate includes: After the pile body stands still for the first preset duration, a number of detection bands are evenly divided along the radial direction of the pile body of the pile body, and a number of test points are set on each detection band; Adopt the double-sided cross-measurement method, fix the transmitting transducer and the receiving transducer at the test points of adjacent detection bands respectively, collect the first wave amplitudes of each test point, and obtain the arithmetic mean value of the first wave amplitudes of the test points of the pile body, which is recorded as the initial inspection amplitude; Then, after the pile body stands still for the second preset duration, repeat the amplitude measurement at the same test points, and obtain the arithmetic mean value of the first wave amplitudes of the test points after standing still for the second preset duration, which is recorded as the re-inspection amplitude; The amplitude recovery rate is the ratio of the re-inspection amplitude to the initial inspection amplitude.

[0013] Further, secondarily determine whether the preparation of the pile body meets the preset standard according to the waveform characterization value of the pile body, where if the waveform characterization value is less than the preset waveform characterization value, it is determined that the preparation of the pile body does not meet the preset standard; if the waveform characterization value is greater than or equal to the preset waveform characterization value, it is determined that the preparation of the pile body meets the preset standard, and the cap is poured; The waveform characterization value is the ratio between the number of ultrasonic waveform peaks whose maximum value is greater than or equal to the preset peak value and the total number.

[0014] Further, determine whether the preparation of the cap meets the preset standard according to the compactness characterization value of the cap, where if the compactness characterization value is less than the first preset compactness characterization value, it is determined that the preparation of the cap meets the preset standard; If the compactness characterization value is greater than or equal to the first preset compactness characterization value and less than the second preset compactness characterization value, it is determined that the preparation of the bearing platform does not meet the preset standard, and the pouring rate of the concrete of the bearing platform is reduced according to the difference between the compactness characterization value and the first preset compactness characterization value; If the compactness characterization value is greater than or equal to the second preset compactness characterization value, it is determined that the preparation of the bearing platform does not meet the preset standard, and it is determined that the reason for the non - compliance of the preparation of the bearing platform with the preset standard is that the bearing platform has a penetrating defect, the preparation is aborted and a warning is issued; The penetrating defect includes one or more of the following: the bearing platform has a cavity phenomenon, or, the bearing platform has a mud - inclusion phenomenon, or, the bearing platform has a honeycomb structure.

[0015] Further, the reduction amplitude of the pouring rate of the concrete of the bearing platform is positively correlated with the compactness characterization difference, where the compactness characterization difference is the difference between the compactness characterization value and the first preset compactness characterization value.

[0016] Further, the process of obtaining the compactness characterization value of the bearing platform includes: A number of ultrasonic detection tubes are uniformly arranged during the pouring process of the bearing platform; Using a multi - channel ultrasonic detector, synchronously exciting the transmitting transducers of each detection tube, recording the first - arrival wave velocity values of each detection tube, and obtaining the arithmetic mean of the first - arrival wave velocity values of each detection tube; According to the arithmetic mean of the first - arrival wave velocity values of each detection tube, the standard deviation of the first - arrival wave velocity value of the bearing platform is obtained, which is denoted as the compactness characterization value of the bearing platform.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: by setting the associated detection of the static time of the pile body and the final setting time of the concrete, and combining the dual inspections of the energy attenuation characterization value and the wave amplitude recovery rate, the present invention effectively distinguishes the false wave amplitude attenuation caused by the non - final setting of the concrete from the real pile foundation structure defects, avoiding detection misjudgment; introducing a hierarchical warning mechanism based on the standard deviation of sound velocity during the construction stage of the bearing platform, and preventing the formation of penetrating defects such as honeycomb structures or cavities by dynamically regulating the pouring rate or aborting the construction, realizing the intelligent control of the preparation quality of the pile foundation and the bearing platform, achieving the self - adaptive adjustment of the construction process and the precise positioning of defects, thereby improving the detection accuracy.

[0018] Further, the present invention uses the wave amplitude standard deviation as the quantization basis of the energy attenuation characterization value, realizes the objective evaluation of the pile body uniformity defect, reflects the discreteness of the wave amplitudes in different detection zones, precisely locates local defects, and the standard deviation index is more sensitive to abnormal wave amplitude values, thus avoiding the uniformity defect being masked by the overall arithmetic mean.

[0019] Furthermore, the present invention ensures the synchronization of ultrasonic detection with the final setting state of concrete by setting the static detection for the first preset duration and the interval determination of the energy attenuation characterization value, and verifying through the re-inspection for the second preset duration, avoiding the false defect determination caused by insufficient static duration, thereby improving the detection accuracy of the pile foundation.

[0020] Furthermore, the present invention has several frequency increasing methods for increasing the vibration frequency of the pile body, and each frequency increasing method has a different amplitude increase for the vibration frequency of the pile body, thereby realizing the precise control of the amplitude increase of the vibration frequency of the pile body.

[0021] Furthermore, when the compactness characterization value is between the first and second preset values, it is determined that the local compactness is insufficient, and the concrete fluidity is optimized by reducing the pouring rate; when the compactness characterization value is greater than or equal to the second preset value, it is determined that there is a through defect, and the construction is immediately stopped and a warning is given to avoid the expansion of the defect and reduce the later rework cost, thereby realizing hierarchical warning.

[0022] Furthermore, the compactness characterization value calculated based on the standard deviation of the sound velocity can sensitively reflect the abnormality of the internal uniformity of the bearing platform, thereby realizing the precise positioning of the cause of the defect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flowchart of the pile foundation detection method based on ultrasonic waves according to an embodiment of the present invention; Figure 2 is a flowchart for determining whether the preparation of the pile body meets the preset standard according to the energy attenuation characterization value in an embodiment of the present invention; Figure 3 is a flowchart for determining the reason why the preparation of the pile body does not meet the preset standard in an embodiment of the present invention; Figure 4 is a flowchart for determining whether the preparation of the bearing platform meets the preset standard in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] In order to make the objectives and advantages of the present invention clearer, the present invention will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and do not limit the protection scope of the present invention.

[0026] It should be noted that the data in this embodiment are obtained through comprehensive analysis and evaluation of the historical detection data and corresponding historical detection results of the present invention in the three months before this detection. Those skilled in the art can understand that the method for determining a single above-mentioned parameter in the present invention can be to select the value with the highest proportion according to the data distribution as the preset standard parameter, use weighted summation to obtain the value as the preset standard parameter, substitute each historical data into a specific formula and use the value obtained by the formula as the preset standard parameter, or other selection methods, as long as it satisfies that the method of the present invention can clearly define different specific situations in the single-item determination process through the obtained value.

[0027] Please refer to Figure 1 、 Figure 2 、 Figure 3 and Figure 4 as shown, which are the flowcharts of the pile foundation detection method based on ultrasonic waves in the embodiment of the present invention; the flowchart of determining whether the preparation of the pile body meets the preset standard according to the energy attenuation characterization value in the embodiment of the present invention; the flowchart of determining the reason why the preparation of the pile body does not meet the preset standard in the embodiment of the present invention; the flowchart of determining whether the preparation of the bearing platform meets the preset standard in the embodiment of the present invention.

[0028] The embodiment of the present invention provides a pile foundation detection method based on ultrasonic waves, which is characterized by including: Step S1, after the pile body is prepared, it is left static for the first preset duration of 8h, ultrasonic detection is carried out, several wave amplitudes of the pile body provided with several detection bands are obtained, and the energy attenuation characterization value is obtained; Step S2, when it is determined according to the energy attenuation characterization value that the preparation of the pile body does not meet the preset standard, the waveform peak value of the ultrasonic first wave is collected, the waveform characterization value is obtained, and after the pile body is left static for the second preset duration of 11h, several wave amplitudes of several detection bands evenly distributed along the radial direction of the pile body are obtained, and the wave amplitude recovery rate is obtained; Step S3, when it is determined according to the energy attenuation characterization value that the preparation of the pile body does not meet the preset standard, it is determined again whether the preparation of the pile body meets the preset standard according to the waveform characterization value, or the reason why the preparation of the pile body does not meet the preset standard is determined according to the wave amplitude recovery rate, and the reasons include that there are holes in the pile body or the energy attenuation characterization value has a deviation; Step S4, when it is determined according to the energy attenuation characterization value that the preparation of the pile body meets the preset standard, the bearing platform is poured; Step S5, the sound velocity of each detection point of the bearing platform is obtained, the compactness characterization value of the bearing platform is obtained, and when it is determined according to the compactness characterization value that the preparation of the bearing platform does not meet the preset standard, the concrete pouring rate is reduced or the pouring is stopped and a warning is issued.

[0029] In this embodiment, the value range of the first preset duration is (5h, 10h), and the value range of the second preset duration is (6h, 12h). Preferably, the first preset duration is selected as 8h, and the second preset duration is selected as 11h.

[0030] Specifically, it is determined whether the preparation of the pile meets the preset standard according to the energy attenuation characterization value, where if the energy attenuation characterization value is less than the first preset energy attenuation characterization value of 0.8 dB, it is determined that the preparation of the pile meets the preset standard and the cap pouring is carried out; if the energy attenuation characterization value is greater than or equal to the first preset energy attenuation characterization value and less than the second preset energy attenuation characterization value of 1.2 dB, it is determined that there is a tendency for the preparation of the pile not to meet the preset standard, and it is determined again whether the preparation of the pile meets the preset standard according to the waveform characterization value; if the energy attenuation characterization value is greater than or equal to the second preset energy attenuation characterization value, it is determined that the preparation of the pile does not meet the preset standard, and the reason why the preparation of the pile does not meet the preset standard is determined according to the wave amplitude recovery rate.

[0031] Specifically, the energy attenuation characterization value is the standard deviation of the wave amplitudes corresponding to a number of test points, where the test points are all arranged on the detection bands evenly distributed in several radial directions along the pile body.

[0032] In this embodiment, the value range of the first preset energy attenuation characterization value is (0.5 dB, 0.9 dB), and the value range of the second preset energy attenuation characterization value is (1.0 dB, 1.3 dB). Preferably, the first preset energy attenuation characterization value is selected as 0.8 dB, and the second preset energy attenuation characterization value is selected as 1.2 dB.

[0033] Specifically, by calculating the standard deviation of the wave amplitudes of the detection points evenly distributed in the radial direction of the pile body as the energy attenuation characterization value, the uniformity of the concrete distribution along the pile body can be objectively reflected, avoiding misjudgment caused by the abnormality of a single detection point. Through the comparison between the energy attenuation characterization value and the preset characterization value, a hierarchical control mechanism is realized, thereby improving the test accuracy.

[0034] Specifically, the reason why the preparation of the pile does not meet the preset standard is determined according to the wave amplitude recovery rate of the pile body, where if the wave amplitude recovery rate is less than the preset wave amplitude recovery rate of 1.15, it is determined that the reason why the preparation of the pile does not meet the preset standard is that there are holes in the pile body, and the vibration frequency of the pile body is increased according to the difference between the wave amplitude recovery rate and the preset wave amplitude recovery rate; If the wave amplitude recovery rate is greater than or equal to the preset wave amplitude recovery rate, it is determined that the reason for the preparation of the pile body not meeting the preset standard is that the first preset duration is less than the final setting duration of the concrete of the pile body, resulting in deviation of the energy attenuation characterization value obtained by ultrasonic testing. In fact, the preparation of the pile body meets the preset standard.

[0035] In this embodiment, the arithmetic mean value of the wave amplitude recovery rates obtained from a large number of qualified pile foundation tests is taken, but the above value is not limited to this, and those skilled in the art can also adjust this value according to actual needs.

[0036] Specifically, several frequency increase methods are set for increasing the vibration frequency of the pile body. Among them, If the difference in wave amplitude recovery rate is less than the first preset difference in wave amplitude recovery rate of 0.35, the vibration frequency of the pile body is increased to the corresponding value using the first frequency adjustment coefficient of 1.02; If the difference in wave amplitude recovery rate is greater than or equal to the first preset difference in wave amplitude recovery rate and less than the second preset difference in wave amplitude recovery rate of 0.55, the vibration frequency of the pile body is increased to the corresponding value using the second frequency adjustment coefficient of 1.04; If the difference in wave amplitude recovery rate is greater than or equal to the second preset difference in wave amplitude recovery rate, the vibration frequency of the pile body is increased to the corresponding value using the third frequency adjustment coefficient of 1.06; The difference in wave amplitude recovery rate is the difference between the wave amplitude recovery rate and the preset wave amplitude recovery rate.

[0037] Specifically, the process of obtaining the wave amplitude recovery rate includes: After the pile body is static for the first preset duration, several detection bands are evenly divided along the radial direction of the pile body of the pile body, and several test points are set on each detection band; Using the double-sided cross-measurement method, the transmitting transducer and the receiving transducer are respectively fixed at the test points corresponding to the detection bands on both sides of the pile body, and the first wave amplitudes of each test point are collected through a digital ultrasonic detector, and the arithmetic mean value of the first wave amplitudes of the test points of the pile body is obtained and recorded as the initial inspection amplitude; Then, after the pile body is static for the second preset duration, the wave amplitude measurement is repeated at the same test points, and the arithmetic mean value of the first wave amplitudes of the test points after the second preset duration of static is obtained and recorded as the re-inspection amplitude; The wave amplitude recovery rate is the ratio of the re-inspection amplitude to the initial inspection amplitude.

[0038] The first wave refers to the earliest recognizable waveform captured by the transmitting transducer and the receiving transducer when ultrasonic waves propagate in the concrete medium.

[0039] The first wave amplitude refers to the maximum vertical distance between the first wave peak and the waveform reference line when ultrasonic waves propagate in the concrete medium. In this embodiment, a digital ultrasonic detector is used to obtain it.

[0040] Specifically, according to the waveform characterization value of the pile body, it is determined secondly whether the preparation of the pile body meets the preset standard, where if the waveform characterization value is less than 0.75 of the preset waveform characterization value, it is determined that the preparation of the pile body does not meet the preset standard; if the waveform characterization value is greater than or equal to the preset waveform characterization value, it is determined that the preparation of the pile body meets the preset standard, and the casting of the bearing platform is carried out; The waveform characterization value is the ratio between the number of ultrasonic waveform peak values greater than or equal to the preset peak value of 60 mV and the total number.

[0041] Specifically, the peak value of the wave reflects the ultrasonic energy transmission efficiency and is positively correlated with the uniformity of the concrete.

[0042] Specifically, according to the compactness characterization value of the bearing platform, it is determined whether the preparation of the bearing platform meets the preset standard, where if the compactness characterization value is less than the first preset compactness characterization value of 0.12 km / s, it is determined that the preparation of the bearing platform meets the preset standard; if the compactness characterization value is greater than or equal to the first preset compactness characterization value and less than the second preset compactness characterization value of 0.35 km / s, it is determined that the preparation of the bearing platform does not meet the preset standard and the casting rate of the concrete of the bearing platform is reduced according to the difference between the compactness characterization value and the first preset compactness characterization value; if the compactness characterization value is greater than or equal to the second preset compactness characterization value, it is determined that the preparation of the bearing platform does not meet the preset standard, and it is determined that the reason for the non - compliance of the preparation of the bearing platform is that there are penetrating defects in the bearing platform, the preparation is aborted and a warning is issued; The penetrating defects include one or more of the following: the bearing platform has a cavity phenomenon, or, the bearing platform has a mud - inclusion phenomenon, or, the bearing platform has a honeycomb structure.

[0043] In this embodiment, the first preset compactness characterization value is taken as 0.12 km / s, and the second preset compactness characterization value is taken as 0.35 km / s, but the above values are not limited to this, and those skilled in the art can also adjust the values according to actual needs.

[0044] Specifically, the reduction amplitude of the casting rate of the concrete of the bearing platform is positively correlated with the difference in compactness characterization, where the positive correlation is, for example, a linear positive correlation or a non - linear positive correlation. The linear slope of the linear positive correlation is not specifically limited. It can be understood that the greater the difference in compactness characterization, the greater the reduction amplitude of the casting rate of the concrete of the bearing platform; the difference in compactness characterization is the difference between the compactness characterization value and the first preset compactness characterization value.

[0045] Specifically, the process of obtaining the compactness characterization value of the bearing platform includes: A number of ultrasonic detection tubes are evenly arranged during the pouring process of the bearing platform; Using a multi-channel ultrasonic detector, synchronously exciting the transmitting transducers of each detection tube, recording the first-wave sound velocity values of each detection tube, and obtaining the arithmetic mean of the first-wave sound velocity values of each detection tube; According to the arithmetic mean of the first-wave sound velocity values of each detection tube, obtaining the standard deviation of the first-wave sound velocity value of the bearing platform, denoted as the compactness characterization value of the bearing platform.

[0046] So far, the technical solution of the present invention has been described in combination with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0047] The above are only the preferred embodiments of the present invention and are not used to limit the present invention; for those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A pile foundation detection method based on ultrasonic wave, characterized in that: include: After the pile body is prepared, it is left to stand for a first preset time, and ultrasonic testing is performed to obtain a number of amplitudes of the pile body provided with a number of testing bands, and an energy attenuation characterization value is obtained; When it is determined according to the energy attenuation characterization value that the preparation of the pile body does not meet the preset standard, the peak value of the waveform of the first ultrasonic wave is collected and the waveform characterization value is obtained, and the pile body is left to stand for a second preset time to obtain the amplitude of the pile body and obtain the amplitude recovery rate; Secondarily determining whether the preparation of the pile body meets the preset standard according to the waveform characterization value, or determining the reason why the preparation of the pile body does not meet the preset standard according to the amplitude recovery rate, the reason including the presence of holes in the pile body or the deviation of the energy attenuation characterization value; When the preparation of the pile body is judged to meet the preset standard according to the energy attenuation characterization value, the cap casting is carried out; The sound velocity of each detection point of the foundation is obtained to obtain the density characterization value of the foundation. When it is determined that the preparation of the foundation does not meet the preset standard according to the density characterization value, the concrete pouring rate is reduced or the pouring is stopped and an early warning is issued.

2. The ultrasonic pile foundation detection method according to claim 1, characterized in that: The energy attenuation characterization value is used to determine whether the preparation of the pile body meets the preset standard, wherein: If the energy attenuation characterization value is less than the first preset energy attenuation characterization value, it is determined that the preparation of the pile body meets the preset standard and the cap casting is performed; If the energy attenuation characterization value is greater than or equal to the first preset energy attenuation characterization value and less than the second preset energy attenuation characterization value, it is determined that the preparation of the pile body has a tendency not to meet the preset standard, and a second determination is made based on the waveform characterization value whether the preparation of the pile body meets the preset standard; If the energy attenuation characterization value is greater than or equal to the second preset energy attenuation characterization value, it is determined that the preparation of the pile body does not meet the preset standard, and the reason why the preparation of the pile body does not meet the preset standard is determined according to the amplitude recovery rate.

3. The ultrasonic pile foundation detection method according to claim 2, characterized in that: The energy attenuation characterization value is the standard deviation of the amplitude corresponding to a number of test points, wherein the test points are all arranged on a number of radially uniformly distributed detection zones of the pile body along the pile body.

4. The ultrasonic-based pile foundation detection method according to claim 3, characterized in that: The reason why the preparation of the pile body does not meet the preset standard is determined according to the amplitude recovery rate of the pile body, wherein: If the amplitude recovery rate is less than the preset amplitude recovery rate, it is determined that the reason why the preparation of the pile body does not meet the preset standard is that holes appear in the pile body, and the vibration frequency of the pile body is increased according to the difference between the amplitude recovery rate and the preset amplitude recovery rate; If the amplitude recovery rate is greater than or equal to the preset amplitude recovery rate, it is determined that the reason why the preparation of the pile body does not meet the preset standard is that the first preset time is less than the final setting time of the concrete of the pile body, resulting in a deviation in the energy attenuation characterization value obtained by ultrasonic testing.

5. The ultrasonic-based pile foundation detection method according to claim 4, characterized in that: In order to increase the vibration frequency of the pile body, several frequency increasing methods are provided and each frequency increasing method increases the vibration frequency of the pile body by a different amplitude.

6. The ultrasonic-based pile foundation detection method according to claim 5, characterized in that: The process of obtaining the amplitude recovery rate includes: After the pile body is left to stand for a first preset time, a plurality of detection zones are evenly divided along the radial direction of the pile body, and each detection zone is provided with a plurality of test points; The double-sided measurement method is adopted, the transmitting transducer and the receiving transducer are respectively fixed at the test points of the adjacent detection bands, the first wave amplitude of each test point is collected, and the arithmetic mean of the first wave amplitude of the test point of the pile body is obtained, which is recorded as the initial test amplitude; Then, after the pile body is left to stand for a second preset time, the amplitude measurement is repeated at the same test point to obtain the arithmetic mean of the first wave amplitudes of the test points after the pile body is left to stand for the second preset time, which is recorded as the retest amplitude; The amplitude recovery rate is the ratio of the re-test amplitude to the initial test amplitude.

7. The ultrasonic-based pile foundation detection method according to claim 6, characterized in that: A secondary determination is made as to whether the preparation of the pile body meets the preset standard according to the waveform characterization value of the pile body, wherein: If the waveform characterization value is less than the preset waveform characterization value, it is determined that the preparation of the pile body does not meet the preset standard; If the waveform characterization value is greater than or equal to the preset waveform characterization value, it is determined that the preparation of the pile body meets the preset standard, and the cap casting is carried out; The waveform characterization value is the ratio between the number of ultrasonic waveform peak values ​​that are greater than or equal to the preset peak value and the total number.

8. The ultrasonic-based pile foundation detection method according to claim 7, characterized in that: According to the density characterization value of the foundation, it is determined whether the preparation of the foundation meets the preset standard, wherein: If the density characterization value is less than the first preset density characterization value, it is determined that the preparation of the foundation meets the preset standard; If the density characterization value is greater than or equal to the first preset density characterization value and less than the second preset density characterization value, it is determined that the preparation of the cap does not meet the preset standard and the pouring rate of the concrete of the cap is reduced according to the difference between the density characterization value and the first preset density characterization value; If the density characterization value is greater than or equal to the second preset density characterization value, it is determined that the preparation of the foundation does not meet the preset standard, and the reason why the preparation of the foundation does not meet the preset standard is that the foundation has a penetration defect, the preparation is terminated and an early warning is issued; The through-continuity defects include one or more of the following: voids appear in the foundation, mud inclusions appear in the foundation, and a honeycomb structure appears in the foundation.

9. The ultrasonic-based pile foundation detection method according to claim 8, characterized in that: The reduction range of the pouring rate of the concrete of the foundation is positively correlated with the density characterization difference, wherein the density characterization difference is the difference between the density characterization value and the first preset density characterization value.

10. The ultrasonic-based pile foundation detection method according to claim 9, characterized in that: The process of obtaining the compactness characterization value of the foundation includes: During the pouring process of the cap, a number of ultrasonic detection tubes are evenly arranged; A multi-channel ultrasonic detector is used to synchronously excite the transmitting transducers of each detection tube, record the first wave sound velocity value of each detection tube, and obtain the arithmetic mean of the first wave sound velocity value of each detection tube; According to the arithmetic mean of the first wave sound velocity values ​​of each detection tube, the standard deviation of the first wave sound velocity value of the foundation is obtained and recorded as the density characterization value of the foundation.

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